Lubricated automotive vacuum pump

ABSTRACT

A lubricated automotive vacuum pump which provides a low-pressure for an automotive actuator includes a static pump housing which houses a pump chamber radially defined by a chamber surface, a pump rotor having a cylindrical rotor bearing surface and a rotor body having a vane slit, a vane which is shiftably supported by and radially shiftable in the vane slit and which separates the pump chamber into rotating compartments, a friction bearing which rotatably supports the pump rotor at the static pump housing, a pump gas inlet and outlet, an oil inlet channel which provides lubrication oil to the pump rotor, a separate oil outlet opening arranged at the rotor body, and a switchover valve for temporarily connecting the separate oil outlet opening with an oil drain. The friction bearing is defined by a cylindrical stator friction bearing surface and by the cylindrical rotor bearing surface.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/069022, filed on Aug. 19, 2015. The International Application was published in English on Feb. 23, 2017 as WO 2017/028914 Al under PCT Article 21(2).

FIELD

The present invention relates to a lubricated automotive vacuum pump for providing low-pressure to an automotive actuator.

BACKGROUND

An automotive vacuum pump provides low-pressure of less than absolute 500 mbar for one or more automotive actuators, for example, for a pneumatic brake power assist unit. The vacuum pump is lubricated with oil for reducing mechanical wear, improving the pneumatic efficiency, and dissipating heat.

The liquid lubricant flows into the pump chamber where at least one rotating vane separates the pump chamber into several rotating compartments. The pump chamber of conventional vacuum pumps is provided with a gas outlet opening which is fluidically connected to a pump gas outlet. If the pump chamber is not provided with a separate oil outlet opening, the liquid lubricant is pumped out of the pump chamber together with the compressed air. The vacuum pump can alternatively be provided with a separate static oil outlet opening at the chamber housing. The oil outlet opening is located in the final compression sector. The oil outlet channel can be provided with a check valve so that the oil outlet channel is only open if the fluidic pressure is above a particular threshold pressure and the oil outlet channel only opens in the final compression phase.

The pressure situation and the pressure level in the pump chamber can be very different and in particular depends on the total pressure at the pump gas inlet which can be in a range of 1000 mbar to 100 mbar. The check valve generally opens at the same pressure difference, however, so that an optimized opening moment of the check valve cannot be realized for all pressure situations. The mechanical check valve causes noise and can generally be damaged.

SUMMARY

An aspect of the present invention is to provide a lubricated automotive vacuum pump with an improved lubrication oil removal.

In an embodiment, the present invention provides a lubricated automotive vacuum pump for providing a low-pressure for an automotive actuator. The lubricated automotive vacuum pump includes a static pump housing configured to house a pump chamber, the pump chamber being radially defined by a circumferential chamber surface, a pump rotor configured to rotate around an axial rotation axis, the pump rotor comprising a cylindrical rotor bearing surface and a rotor body which comprises a vane slit, a vane which is configured to be shiftably supported by and radially shiftable in the vane slit and to separate the pump chamber into rotating compartments, a friction bearing configured to rotatably support the pump rotor at the static pump housing, a pump gas inlet, a pump gas outlet which is separate from the pump gas inlet, an oil inlet channel configured to provide a lubrication oil to the pump rotor, at least one separate oil outlet opening arranged at the rotor body, and an automatic mechanical switchover valve for temporarily connecting the at least one separate oil outlet opening with an oil drain. The friction bearing is defined by a cylindrical stator friction bearing surface of the static pump housing and by the cylindrical rotor bearing surface of the pump rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a longitudinal section of a lubricated automotive vacuum pump including two oil outlet openings and a mechanical switchover valve;

FIG. 2 shows enlarged one oil outlet opening and the mechanical switchover valve of the vacuum pump of FIG. 1;

FIG. 3 shows a top view of the vacuum pump of FIG. 1 without a cover lid;

FIG. 4 shows a side view of the vacuum pump of FIG. 1; and

FIG. 5 shows a cross section V-V of the vacuum pump of FIG. 1.

DETAILED DESCRIPTION

The lubricated automotive vacuum pump comprises a pump housing which houses a pump chamber which is radially defined by a circumferential chamber surface. The vacuum pump also is provided with a pump rotor which rotates around an axial rotation axis. The pump rotor is provided with a rotatable rotor body which supports at least one shiftable vane in a corresponding vane slit. The vane or the vanes separate the pump chamber into several rotating pump compartments. The vacuum pump is provided with a friction bearing for rotatably supporting the pump rotor at the static pump housing. The friction bearing can, for example, be provided at one axial end portion of the rotor body of the pump rotor. The friction bearing is defined by a hollow cylindrical stator friction bearing surface of the pump housing and a corresponding cylindrical rotor bearing surface of the pump rotor.

The vacuum pump is provided with a pump gas inlet and a separate pump gas outlet. The pump gas outlet is fluidically connected to a gas outlet opening at the pump chamber. The gas outlet opening is provided in a compression sector of the pump chamber where the rotating compartment volume of the rotating compartment decreases when the pump rotor rotates.

The vacuum pump is provided with a lubricant oil inlet channel for providing lubrication oil to the pump rotor. Lubrication oil is provided through the inlet channel to the pump rotor to provide lubrication of the friction bearing and to, for example, provide lubrication to the pump chamber to lubricate the clearances between the rotating parts and the non-rotating parts of the pump chamber.

The vacuum pump is provided with a separate oil outlet opening at the rotor body and is also provided with an automatic mechanical switchover valve for temporarily connecting the oil outlet opening with an oil drain. The oil outlet opening opens to the pump chamber. The oil outlet opening is not static at the pump housing, but is provided to co-rotate with the pump rotor. The oil outlet channel leading from the oil outlet opening to the oil drain is not always open, but is provided with a switchover valve which temporarily and repetitively opens so that oil can only be dissipated from the pump chamber in particular and defined rotor positions. The switching of the automatic mechanical switchover valve is only caused by the rotor rotation. The switchover mechanism can generally be of any kind which opens and closes the switchover valve dependent on the rotational rotor position. The opening and closing of the oil outlet channel therefore no longer depends on the pressure situation. An additional check valve can, however, be provided in the oil outlet channel.

The oil outlet opening co-rotates with the corresponding rotating compartment so that the fluidic dynamics of the outflowing oil is improved. The automatic mechanical switchover valve is reliable and does not cause mechanical noise. An automatic mechanical switchover valve can also have a simple structure which can be produced cost-effectively.

In an embodiment of the present invention, one oil outlet opening can, for example, be provided for each respective rotating compartment so that each rotating compartment is provided with its own corresponding oil outlet opening. If two compartments are provided, two oil outlet openings are provided, one oil outlet opening for each compartment.

In an embodiment of the present invention, the switchover valve can, for example, be defined by a rotor valve opening at the rotor body and a stator valve opening at the pump housing. The rotor valve opening and the stator valve opening are in-line with each other, namely, in fluidic connection, when the switchover valve is open. The switchover valve is closed as long as the rotor valve opening and the stator valve opening are not in fluidic connection with each other. The switching status of the switchover valve is only defined by the rotational rotor position. The mechanical switchover valve is simple and reliable.

In an embodiment of the present invention, the rotor valve opening and the stator valve opening can, for example, be provided at the cylindrical friction bearing surfaces. The friction bearing surfaces define a very small cylindrical gap between them so that, in the closed switching status of the switchover valve, the valve's sealing quality is very good so that no relevant fluid flow is possible when the switchover valve is closed.

In an embodiment of the present invention, the oil outlet opening can, for example, be defined by an axial bridge groove at the rotor body. The bridge groove generally has an axial component or is exactly provided in an axial direction. The rotor valve opening can alternatively or additionally be defined by the axial bridge groove at the rotor body. A separate axial bridge groove is provided in the rotor body for every oil outlet opening. A groove in the rotor body is simple, and manufacturing of the bridge groove can be provided cost-effectively.

In an embodiment of the present invention, the stator valve opening can, for example, be defined by one single stator groove. The stator groove can, for example, be provided with an axial orientation. The respective end portions of the axial rotor bridge grooves and of the static stator groove can, for example, define the respective valve openings being in-line in the open switching status of the switchover valve. In other words, the rotor grooves and the stator groove axially overlap in part when the grooves are rotationally in-line with each other.

In an embodiment of the present invention, the oil outlet opening can, for example, be provided in the lagging third of the respective compartment, for example, in the lagging fifth of the respective compartment. The lagging third of the respective compartment is the sector of the respective compartment which arrives at the separation section the latest. The separation section of the vacuum pump causes a fluidic separation of the rotating compartment into a compression part and a suction part. In the separation section, the rotor body is provided adjacent to the circumferential chamber surface so that no relevant fluid flow in circumferential direction is possible through the separation section. The oil outlet opening can, for example, be provided, as seen in a circumferential direction, adjacent to the vane slit, namely, in a distance of less than 10 mm as seen in circumferential direction from the vane slit.

In an embodiment of the present invention, the stator groove can, for example, be provided within 30° of the separation section.

An embodiment of the present invention is described below under reference to the drawings.

The drawings show a lubricated automotive vacuum pump 10 for providing pneumatic low-pressure for an automotive actuator. The vacuum pump 10 is a mechanical vacuum pump which is mechanically driven by an automotive engine.

The vacuum pump 10 is provided with a metal pump housing 12 which is basically defined by the two housing parts, namely, a pot-shaped housing body 20 and a cover lid 14. The pump housing 12 surrounds a pump chamber 16 and also defines a cylindrical stator friction bearing surface 52 of a rotor friction bearing 50.

The vacuum pump 10 is provided with a pump rotor 30 which rotates around an axial rotation axis 13. The pump rotor 30 is provided with a cylindrical rotor body 32 which is provided with a radial vane slit 34 which supports a vane 36 which is radially shiftable in the vane slit 34. The rotor body 32 is also provided with a cylindrical rotor friction bearing surface 51 which together with the stator friction bearing surface 52 defines a friction bearing 50 at one axial end of the pump rotor 30. The same axial end of the pump rotor 30 is provided with a coupling structure 62 for mechanically coupling a drive of the automotive engine.

The pump housing 12 and the pump rotor 30 together define the sickle-shaped pump chamber 16 which is laterally defined by a circumferential chamber surface 22, the proximal cylindrical surface 31 defined by the rotor body 32, by a sickle-shaped chamber bottom surface 23 and by an identical sickle-shaped top surface defined by the inside of the cover lid 14.

The sickle-shaped pump chamber 16 is divided by the vane 36 into two separate rotating compartments 161, 162 which rotate when the pump rotor 30 rotates. The rotor body 32 is arranged adjacent to the circumferential chamber surface 22 in a separation section 163 of the pump chamber 16 so that no relevant gas flow in circumferential direction is possible.

The vacuum pump 10 is provided with a gas inlet 15 which is connectable to an automotive actuator, for example, to a pneumatic brake assistance unit, and with a gas outlet 38 which is fluidically connected to the atmospheric pressure of the atmosphere. The gas outlet 38 is defined by a gas outlet opening 37 in the circumferential chamber surface 22 and by a check valve 39 arranged fluidically downstream of the gas outlet opening 37 and provided at the outside of the pot-shaped housing body 20. The gas outlet can alternatively be provided at another pumping chamber wall, for example, at the chamber bottom surface.

As can best be seen in FIG. 5, the vacuum pump 10 is provided with an oil inlet channel 60 which is connected to an external oil pump 11. The external oil pump 11 provides a pressurized lubricant oil which is pumped via the oil inlet channel 60 to the friction bearing 50 from where the oil flows axially to the pump chamber 16.

The rotor body 32 is provided with two axial bridge grooves 421, 422 at the cylindrical surface of the rotor body 32. The pot-shaped housing body 20 is provided with one single axial stator groove 44 in the cylindrical friction bearing surface 52. The axial extent of the two axial bridge grooves 421, 422 reaches from the pump chamber 16 into the friction bearing 50. The axial extent of the axial stator groove 44 covers most of the axial length of the friction bearing 50. The axial bridge grooves 421, 422 and the axial stator groove 44 axially overlap in part so that the overlapping portions of the axial bridge grooves 421, 422 and of the axial stator groove 44 define rotor valve openings 821, 822 and a stator valve opening 80 which together define an automatic mechanical switchover valve 40, respectively. The upper end portion of the axial bridge grooves 421, 422 define two separate oil outlet openings 411, 412 through which oil in the respective rotating compartment 161 can flow out of the pump chamber 16 if the switchover valve 40 is open. The switchover valve 40 is open if one of the rotor valve openings 821, 822 stand opposite to or is radially in-line with the stator valve opening 80.

A possible spatial orientation of the vacuum pump 10 is shown in FIG. 1. The vacuum pump 10 is mounted and fixed in the respective automobile with a transversal pump plane inclined with respect to the horizontal plane and with a rotational pump orientation so as to provide the oil outlet opening 411 at the lowest point when the switchover valve 40 is open. The spatial orientation of the vacuum pump may, however, differ significantly among the applications. The orientation with respect to the horizontal plane is not particularly significant since the oil drain is provided by the internal pressure of the pump; the effect of the gravity can therefore be considered as marginal.

The open axial end of the axial stator groove 44 defines an oil drain 70 through which the oil coming from the pump chamber 16 and flowing through the respective axial bridge groove 421 and axial stator groove 44 dissipates to atmospheric pressure.

The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 

What is claimed is: 1-8. (canceled)
 9. A lubricated automotive vacuum pump for providing a low-pressure for an automotive actuator, the lubricated automotive vacuum pump comprising: a static pump housing configured to house a pump chamber, the pump chamber being radially defined by a circumferential chamber surface; a pump rotor configured to rotate around an axial rotation axis, the pump rotor comprising a cylindrical rotor bearing surface and a rotor body which comprises a vane slit; a vane which is configured to be shiftably supported by and radially shiftable in the vane slit and to separate the pump chamber into rotating compartments; a friction bearing configured to rotatably support the pump rotor at the static pump housing, the friction bearing being defined by a cylindrical stator friction bearing surface of the static pump housing and by the cylindrical rotor bearing surface of the pump rotor; a pump gas inlet; a pump gas outlet which is separate from the pump gas inlet; an oil inlet channel configured to provide a lubrication oil to the pump rotor; at least one separate oil outlet opening arranged at the rotor body; and an automatic mechanical switchover valve for temporarily connecting the at least one separate oil outlet opening with an oil drain.
 10. The lubricated automotive vacuum pump as recited in claim 9, wherein one of the at least one separate oil outlet opening is provided for each of the rotating compartments.
 11. The lubricated automotive vacuum pump as recited in claim 9, further comprising: a rotor valve opening arranged at the rotor body; and a stator valve opening arranged at the pump housing, wherein, the automatic mechanical switchover valve is defined by the rotor valve opening and by the stator valve opening, and the rotor valve opening and the stator valve opening are arranged so as to be in-line with each other when the automatic mechanical switchover valve is open.
 12. The lubricated automotive vacuum pump as recited in claim 11, wherein the rotor valve opening and the stator valve opening are each provided at the cylindrical stator friction bearing surface and at the cylindrical rotor bearing surface.
 13. The lubricated automotive vacuum pump as recited in claim 11, further comprising: an axial bridge groove arranged at the rotor body, wherein, at least one of the at least one separate oil outlet opening and the rotor valve opening are defined by the axial bridge groove.
 14. The lubricated automotive vacuum pump (10) as recited in claim 11, further comprising: one single stator groove, wherein, the stator valve opening is defined by the one single stator groove.
 15. The lubricated automotive vacuum pump as recited in claim 14, further comprising: a separation section, wherein, the pump chamber is further defined by a cylindrical rotor body chamber surface, the separation section is arranged where the circumferential chamber surface and the cylindrical rotor body chamber surface define a fluidic separation in a circumferential direction, and the one single stator groove is arranged so as to be within 30° of the separation section as seen from the axis of rotation.
 16. The lubricated automotive vacuum pump as recited in claim 15, wherein, the at least one separate oil outlet opening is arranged in a lagging third of a respective one of the rotating compartments, the lagging third being a sector of the respective one of the rotating compartments which arrives at the separation section the latest. 